1. Field of the Invention
The present invention relates to an apparatus and a method for tightening a fixing band, which make it possible to tighten the fixing band to be used, for example, to fix a boot installed to a constant velocity universal joint. The present invention also relates to a constant velocity universal joint apparatus.
2. Description of the Related Art
A constant velocity universal joint has been hitherto used for a driving force-transmitting section of a vehicle such as an automobile in order to transmit the rotary force of a driving shaft to respective axles via a driven shaft. A bellows-shaped boot is installed to the constant velocity universal joint. The boot functions to ensure the liquid-tight performance for lubricating oil enclosed in an outer cup and prevent the inside of the outer cup from invasion of dust, water, and the like.
The boot comprises a bellows section which has a bellows-shaped configuration, a large diameter annular attachment section which is installed to an outer circumferential surface of the outer cup, and a small diameter annular attachment section which is installed to an outer circumferential surface of a shaft on the driven side, wherein the large diameter annular attachment section and the small diameter annular attachment section are formed integrally at both ends of the bellows section. Fixing bands for the large diameter and for the small diameter are constricted to the large diameter annular attachment section and the small diameter annular attachment section respectively.
Usually, such a boot is formed of a rubber material. However, it is difficult to respond to the recent demand, for example, for the high speed durability and the durability against temperature. Therefore, a boot, which is based on the use of a synthetic resin material in place of the rubber material, is often adopted. The boot made of resin has rigidity, and it scarcely suffers from warpage or the like as well, as compared with the boot made of rubber.
A technical concept is disclosed in Japanese Laid-Open Patent Publication No. 7-251336, in which the fixing band is automatically installed by mechanically tightening the fixing band. A band-fixing apparatus, which is disclosed in Japanese Laid-Open Patent Publication No. 7-251336, is provided with a positioning mechanism for the axial direction and a temporary positioning mechanism for the circumferential direction. A method is adopted, in which a projection of the fixing band, which is temporarily positioned at an upper portion of the boot by the temporary positioning mechanism for the circumferential direction, is forcibly nipped and deformed by a pawl mechanism to reduce the diameter of the fixing band so that the boot is fixed to a drive shaft.
That is, the band-fixing apparatus, which is disclosed in Japanese Laid-Open Patent Publication No. 7-251336, is operated such that the projection of the fixing band is sensed by a photoelectric sensor to stop the driving of a motor on the basis of an output of the photoelectric sensor. Accordingly, the position is temporarily determined in the circumferential direction so that the projection of the fixing band is disposed at the upper portion of the boot, and the projection is forcibly nipped and deformed by the aid of the pawl mechanism.
However, in the case of the band-fixing apparatus concerning the conventional technique described above, the projection of the fixing band is forcibly nipped in the state of being temporarily positioned at the upper portion of the boot. Therefore, a problem arises such that it is impossible to make application to an existing tightening apparatus for a fixing band which has been hitherto used by the present applicant.
That is, the present applicant has proposed a method for fixing a boot in which the boot made of rubber is wound with a steel belt, and an overlapped portion of the steel belt is irradiated with a laser beam so that the overlapped portion is welded and fused (see Japanese Patent Publication No. 58-34710). When the method for fixing the boot proposed by the present applicant is applied to a boot made of rubber for a tripod type constant velocity universal joint on the inboard side as shown in FIG. 27, while a boot made of resin is used for a bar field type constant velocity universal joint on the outboard side, then it is demanded that the tightening position for the fixing band for fixing the boot made of resin resides in an identical positional relationship with respect to the position for the welding and fusion effected by radiating the laser beam.
In other words, the laser beam apparatus for welding and fusing the steel belt to the boot made of rubber is arranged in the substantially horizontal direction (lateral direction) with respect to the constant velocity universal joint on the inboard side. Therefore, in view of the layout at the installation place, if the technical concept disclosed in Japanese Laid-Open Patent Publication No. 7-251336 is applied, an inconvenience arises such that the equipment investment is excessive, and the production cost is expensive.
If the technical concept disclosed in Japanese Laid-Open Patent Publication No. 7-251336 is applied, it is necessary to change the existing production line. Also in this viewpoint, the excessive equipment investment is required.
When the boot made of resin is fixed by tightening the fixing band from a position disposed in the substantially horizontal direction (lateral direction) with respect to the constant velocity universal joint on the outboard side, it is demanded that the projection of the fixing band is positioned at a position other than the upper and lower portions of the boot, for example, at a position disposed in the substantially horizontal direction (lateral direction) to tighten the fixing band.
The boot made of resin is produced by means of the blow molding or the injection molding. A plurality of boots made of resin are accommodated and transported in a bucket after the production. For example, a hollow portion of a boot made of resin, which is stacked on the lower side during the transport, is crushed, and a bellows section of the boot made of resin is deformed in some cases, probably because of the following reason. That is, no sufficient cooling time is consumed during the molding process for the resin for the boot made of resin. Therefore, when the plurality of boots made of resin are stacked, then any load is applied to the bellows section, and the bellows section is deformed.
If the fixing band is installed to the boot made of resin deformed as described above by using the band-fixing apparatus concerning the conventional technique described above, the following inconvenience arises as shown in FIG. 43. That is, when the projection of the fixing band is forcibly nipped, the pawl mechanism makes approach to contact with the deformed portion of the bellows section of the boot made of resin. As a result, the bellows section is damaged. When the pawl mechanism contacts with the bellows section, the back and forth movement of the pawl mechanism is obstructed. It is feared that any trouble occurs, for example, such that the operation of the band-fixing apparatus is stopped.
When the large diameter annular attachment section of the boot made of resin is installed to the outer circumferential surface of an outer cup together with the loosely fitted fixing band having a large diameter, and the fixing band having the large diameter is tightened, if the large diameter annular attachment section of the boot made of resin is installed in a state of being deviated from a normal position with respect to the outer circumferential surface of the outer cup, then the following inconvenience arises. That is, the large diameter annular attachment section is fixed by the fixing band in a state in which it is subjected to any positional discrepancy. Similarly, another inconvenience also arises such that the small diameter annular attachment section is fixed by the fixing band in a state in which it is subjected to any positional discrepancy.
The technical concept, in which the projection is provided at a portion at which the fixing band for the boot for the constant velocity universal joint is installed, is disclosed, for example, in Japanese Laid-Open Utility Model Publication No. 1-75629, Japanese Utility Model Publication No. 63-11429, Japanese Utility Model Publication No. 62-16541, and Japanese Utility Model No. 2598540.
In the technical concept disclosed in Japanese Laid-Open Utility Model Publication No. 1-75629, a projection is provided in order to avoid the occurrence of crack at a portion at which a band is installed. In the technical concept disclosed in Japanese Utility Model Publication No. 63-11429, a projection is provided in order to improve the installation performance by giving the flexibility to a boot made of hard resin. In the technical concept disclosed in Japanese Utility Model Publication No. 62-16541, a projection tab is provided in order to improve the strength and the sealing performance. In the technical concept disclosed in Japanese Utility Model No. 2598540, a small projecting strip is provided in order to facilitate the assembling performance by decreasing the rigidity of the fixed end.
As described above, the technical concepts disclosed in these patent documents are completely different from the invention of this application in problem to be solved. Objects, constructions, functions, and effects of them are conspicuously different from those of the invention of this application.
That is, in the technical concepts disclosed in the preceding techniques, the projection is provided in order to improve the tightening force of the fixing band, or the projection is provided, for example, for the purpose of improving the installation performance, improving the sealing performance, or facilitating the assembling performance. On the other hand, the invention of this application is different from the above in the following points. That is, when a fixing band is constricted by using a fixing band-tightening apparatus, the frictional coefficient between a boot made of resin and the fixing band is increased in order to avoid the loose rotation of the fixing band with respect to the boot made of resin. The projection of the fixing band, which may be rotated integrally with the boot made of resin, is forcibly nipped, for example, in a state of being positioned at a position disposed in a substantially horizontal direction. By doing so, the fixing band is tightened and constricted.
In other words, it is enough that a frictional coefficient-increasing mechanism, which is one of the features of the invention of this application, persistently exhibits the function sufficient to integrally rotate the fixing band when the fixing band is constricted by using the fixing band-tightening apparatus. The frictional coefficient-increasing mechanism does not function to increase the tightening force for the fixing band. In this viewpoint, the invention of this application is clearly different from the technical concepts disclosed in the preceding techniques.